Fluid pressure brake apparatus



y 1950 N. G. CADMAN FLUID PRESSURE BRAKE APPARATUS Filed May 22, 1947 mAW N 0 R TA 0 o 7 m T V T 6 a A 0 A on m A m A m g ow B m w mm mm H .onwm m .3 mQm mm I wmwm: N E om 5 @w 5w A v N 3 68m n mm mm mw 9 wm w 8 mmm E m w 9 om 8 wm ow mm NO B Q m Q m Q 9 mm E a 9 K mm 9 2 PatentedJuly 18, 1950 2,515,946 FLUID PRESSURE BRAKE APPARATUS Norman G. Cadman,London, England, assignor, by mesne assignments, to The Westinghouse AirBrake Company, Wilmer-ding, Pa., a corporation of PennsylvaniaApplicationMay 22, 1947,Serial No. 749,732 In Great Britain June 5, 19462 Claims. (Cl. 303-26) This invention relates to fluid pressure brakeapparatus and more particularly to the empty and load type for brakingtractor-trailer vehicles.

One object of the invention is to provide an improved brake equipment ofthe above type.

Another object of the invention is the provision of a tractor-trailerbrake equipment of the above type arranged to be controlled by anoperators control device on the tractor for braking both the tractor andtrailer when the trailer is loaded, and the tractor only when thetrailer is empty.

Another object of the invention is the provision of a brake equipmentsuch as just defined so constructed as to automatically apply the brakeson the trailer, in case a brake control pipe between the tractor andtrailer ruptures, when the the trailer is empty as well as when loaded.

Other objects and advantages will be apparent from the following moredetailed description of a preferred embodiment of the invention takentogether with the accompanying drawing forming a part of thespecification.

Description Referring to the drawing, the single figure is adiagrammatic view, mainly in section, illustrating a preferredembodiment of my invention.

As shown in the drawing, the tractor brake equipment comprises anoperator's control valve device I and a cut-out cock 2 adapted to belocated in the cab of the tractor, a check valve device 3 connected inby-passing relation to the cut-out cock 2, a main reservoir 4 adapted tobe charged with fluid under pressure in any conventional manner and apair of tractor brake cylinders 5 and 6. A brake pipe I extending fromthe operators control valve l is connected through the cut-out cock 2,when it occupies the open position in which it is shown in the drawing,to the rear end of the tractor. A flexible hose connection 8 andcoupling 9 connect the tractor brake pipe I to a corresponding brakepipe ID on the trailer which extends to an automatic control valvedevice ll located on the trailer.

, The trailer brake equipment further comprises a trailer reservoir l2and a pair of trailer brake cylinders l3 and I4.

Considering the parts of the equipment in greater detail, the operator'scontrol valve l comprises a body l5 containing a straight air portion|5a for controlling operation of the tractor brakes and anautomaticportion 18 for controlling operation of the trailer brakes. A manuallyoper- 2 able foot pedal lBa is provided to control operation of thestraight air portion l5a. and the automatic portion I6.

The straight air portion l5a comprises a plug member ll secured in thebody [5 by screwthreaded engagement therewith. The member I! has a borel8 which is coaxial with a bore [9 and a large bore 20 each formed inthe body I5. Slidably mounted in bore 18 is a fluted stem 2| havingformed at one end thereof an exhaust valve 22 which is disposed in achamber 23 formed in body IS. A small passage 24 connects chamber 23 toa chamber 25 formed at the lower end of bore 20. The other end of stem2| extends into a chamber 26, which is adapted to be supplied with fluidunder pressure from main reservoir 4 through a pipe and passage 21, andwherein a supply valve 28 is provided on the end of said stem forcooperation with a seat 29 formed on member I! to control communicationbetween said chamber and chamber 23 to which is connected a pipe 30having branches 30a and 30b leading to the truck brake cylinders 5 and6, respectively. The supply valve 28 is secured to stem 2| by a nut 3|having screw-threaded engagement with said stem. The outer end wall ofchamber 26 is closed by a cap 32 having screwthreaded engagement withthe body l5, and supported by said cap and bearing against valve 28 is aspring 3:3 for urging said valve to a seated position.

Slidably mounted in bore 29 is a piston 34 provided with a stem 35extending through chamber 25 with its end slidably mounted in bore 19.An axial bore 36 extends through piston 34 and stem 35, said bore beingopen at one end to chamber 23 and at the opposite end to a chamber 31formed between the body l5 and a cover member 38. The chamber 31 is opento atmosphere through a slot 39 provided in cover member 38 for the footpedal Ilia. The piston 34 is provided with a packing cup 49 which hassealing and sliding contact with the wall of bore 20 and which isclamped to said piston by a follower 4| and a nut 42havingscrew-threaded engagement with stem 35.

Disposed in bore 20 and chamber 25, between nut 42 and a wall 43,separating chambers 23 and 25, is a spring 44 for urging the end of stem35 out of engagement with exhaust valve 22 to provide a fluid pressurerelease passageway between the tractor brake cylinders 5 and 6 and theatmosphere through pipe 30, chamber 23, bore v 35, chamber 31 and slot39 in cover 38. Disposed at the upper side of piston 34 and be-.

the trailer. '52 by a nut 60 having screw-threaded engagetween saidpiston and a spring cage 45 having a pair of oppositely disposed lugs 86(only one lug being shown in the drawing) is a regulating spring 41 forthe straight air portion I511.

The automatic portion It comprises a plug member 48 secured in the bodyby screwthreaded engagement therewith. The member 48 has a bore 09 whichis coaxial with a bore 50 and a larger bore 5i each formed in the bodyI5. Slidably mounted in the bore 59 is a fluted stem 52 having formed atone end thereof an exhaust valve which is disposed in a chamber 5 5formed in the body [5. A small passage 55 connects chamber 5 1 to achamberfifi. formed at the lower end of bore 5I. The other end of stem52 extends into a chamber 5'Iadapted to be supplied with fluid underpressureiror'n' the main reservoir 5 through the pipe and passage21, andwhich chamber contains a supply valve'58 'provided on the end of saidstem for cooperation witha seat 59 formed on member' lfi'to controlcommunication between said chamber'and chamber 54 to which is connectedbrake pipe 1 leading'to the automatic control valve II located on Supplyv'a1ve'53 is secured to stem ment with said stem. The "outer end wall ofchamber 51 is closed by a cap 6| having screwthreaded engagement withbody I5, and supported by said cap and bearing against valveit58 is aspring 62 for urging said valve to a seated position.

Slidably mounted in bore 5! is a piston 63 provided with a stem 64extending through bore 150 into chamber 54, said piston and stem havingan axial bore 65 open at one end to chamber 54 and open at the oppositeend to chamber 31 which is open to the atmosphere as hereinbeforeexplained. The end of stem 54 is arranged to cooperate with the releasevalved-53 to control communication between bore 65 and chamber 54.

The piston= 03 is provided with a packing cup -66 which has sealing andsliding contact with the wallof bore 5| and which is clamped to sa-idpiston by a follower 61 and anut 58 having screwthreadedengagementwithstem 64.

Formed in body I5 between chambers 54 and 56 is a wall 69 having-formedthereon a 'stop 10 for engagement by the nut -68 to limit downwardmovement of -piston63 and stemt l.

Disposed at the upper side of piston St and between said piston and aspring cage II isa'light spring 12. The spring cage 1I is providedwith aflange 1-3 which rests on the upper end of piston 63 and normallyonastop 14 formed on the body I5. Resting on flange 13 of spring cage 1| isa flange 15 of a second spring cage :16

'having apair of oppositelydisposed lugs 1-1, only one of which is shownin the drawing. Disposed between the flange 15 and the covermemb'er 38is a heavy control-spring 18 for normallymaintaining flange 15 incontact with flange 13 and flange 13 in contact withstop 14 andpiston-63 to hold the piston stem seated against the'exha'ust valve 53and to actuate said valve to open the opposite ends of the lever 19 arebifurcated to straddle respectively, the spring cages A5 and 16, 'oneend of the lever having downwardly opening slots BI to engage the lugs46 onsprin'g cage adapted to be aligned with passages 85 and 86 foropening communication through the brake pipe I, i. e. between the brakepipe sections. A handle 89 is provided for movement from an openposition in which it is shown in the drawing to a position indicated bya dot and dash line 89a to turn the key 81 to a closed position in.which port 88 therein is out of registry with passages 85, 86 forclosing communication through the brake pipe 1.

Disposed in by-passin relation to the cut-out cock 2 is the check valvedevice 3 being connected to the brake pipe 1 by branch pipes '90 and 9|at either side of cut-out cock 2. The check valve device 3 comprises abody "92 having a chamber 93 to which the pipe 901s connected. A bore 94extending through body 92.-is open atone end to chamber 93 and at theopposite end to a chamber 95 formed by body 92 and a cover 96. Disposedin chamber 95 is a-check Valve 91 having a fluted stem '98slidablymounted in bore 95 and arranged to seat on the body around saidbore.

A spring 99 disposed between cover 96 and check valve 91 is provided tourge said valve to its seat.

The automatic control valve device II located on the trailer comprisestwo casing sections I00 and IOI secured to each other and two covers I02and I03 secured to opposite ends of, respectively, said casing sections.CasingsectiontIUI is provided with a large bore I04 which is coaxialwith a small bore I05 also formed in casing section IOI. Slidablymounted in bore I04 is a piston I06 having a-stem I 91 slidably mountedin the smaller bore I05. Piston I06 and stem I91 are provided with anaxial through bore I08. Piston I06 is further provided with a packingcup "I09 which has sealing and sliding contact with the wall of bore I04and which is clamped to said piston by a follower -I I0 and a nut I I Ihaving screw-threaded engagement with stem I01.

Slidablymounted in bore I08 is a rod IIZ, the

upper end'of this rod being provided with a disc I'I3-which is'securedto said rod by a nut I It having screw-threaded engagement with saidrod. The disc H3 is normally held in contact with the upper face ofpiston I06 by a spring I I5 disposed in a chamber 'I I6 formed betweenthe piston I06 and cover I03. 'A 'heavy spring II1, encircling spring 'II5 inchamber I I6, is interposed between piston I06 and cover I03. Thecover'overlaps the adjacent end of bore 104 to provide a stop H8 forengagement by piston I06 to limit the upward movement-thereof. The lowerend of bore 'I 04 terminates in a chamber I I9 which is open to thetrailer brake pipe I!) through a passage I2Iand a chamber I20.

The casing section I00is provided with a bore I22 in coaxial relationwith piston I06 and'open 'at one end 'toa chamber I23 which is connectedto the atmosphere by an exhaust port I 24 and "open'at the opposite endto a chamber I25. Slidably mounted in bore 122 is a piston I26 formed onthe iower end of'rod I I2, said piston havinga stem l21 slidably mountedin a bore I28 connecting chamber "I 25 to a release valve chamber I29,said chambers being also connected by a small passage I39". Chamber I29isco'nr'iected by a pipe I43 and branch pipes I430, and I431) to thetrailer brake cylinders I3'and I4, respectively; Piston I26'and stem I21are provided with an axial bore I 3| for connecting chamber I29 tochamber I23. Piston I 26 is further provided with a packing cup I32which hassealing and sliding contact with the wallof bore I22 and whichis clamped to said piston by a follower I33and a nut I34 havingscrew-threaded engagement with stem I21.

Formed in casing section I99 is a chamber I35 situated beneath chamberI29 and separated therefrom by a plug member I36 having screwthreadedengagement with said casing section. The member I39 has a bore I31 whichis coaxial with the piston stem I21. Slidably mounted in the bore I31 isa fluted stem I39 having formed at one end thereof an exhaust valve I39which is disposed in chamber I29 for seating cooperation with the end ofthe piston stem I21. The other end of stem I39 extends into the chamberI35 wherein a supplyvalve I49 is provided on the end of said stem forcooperation with a seat I4I formed on member I39 to controlcommunication between said chamber, to which trailer reservoir I2 isconnected by a pipe I42, and the chamber I29 to which the trailer brakecylinders I3 and I4 are connected .by a pipe I43 having branches I43aand I431). The supply valve I49 is secured to stem I39 by a nut I44having screw-threaded engagement with said stem. The outer end wall ofchamber I35 is formed by a disc shaped check valve I45 which cooperateswith a seat I46 formed on a rubber gasket I41 disposed between the casinsection I99 and the cover I92. Supported by the check valve I 45. andbearing against the supply valve I40 is a spring I48 for urging each ofsaid valves to a seatedposition.

Operation In operation, let it be assumed that the main reservoir 4 ischarged with fluid under pressure, the cut-out cock 2 is in its openposition in which it is ShOWn in the drawing, and the pedal I60r of theoperators control device I is moved to an elevated or brake releaseposition, in which it is also shown in the drawing, by pressure ofspring 18.

With the pedal I90 in the brake release position spring 41 will beexpanded to permit spring 44 to actuate piston 34 to permit closing ofvalve 28 by spring 33 and to move stem 35 out of engagement with theexhaust valve 22 whereupon the tractor brake cylinders 5 and. 6 will beopen to atmosphere through pipe 39, chamber 23', past the open exhaustvalve 22, through bore 36 in the piston 34 and the stem 35 to chamber 31and thence through the slot 39 in cover 38, whereby the brakes on thetractor will be released.

At the same time the spring I8 will urge flange of spring cage 16against the flange 13 of spring cage H to hold the'latter flange incontact with stop 14, to in turn hold the piSton63 in its lower positionin which the nut 98 engages stop 19. When the piston 63 thus occupiesits lower position, the stern I54 engages the exhaust valve 53 to closecommunication between the brake pipe 1 and the atmosphere. Also when thepiston 63 occupies its lower position it is effective through stems 54and 52 to unseat the supply valve 59 from its seat 59. With the supplyvalve 58 unseated, fluid under pressure from the main reservoir 4 willflow to the brake pipe 1 on the tractor and thence tothe brake pipe I9on the trailer. Fluid under pressureifrom brake pipe I9 flows to "chamsber l29'in theau'to'matic controlivalve II onthe trailer thence past thecheck valve I45 to chamber I35 and from saidchamber through the pipe I42to the trailer reservoir I2 to charge said reservoir to substantiallythe pressure in the brake pipe 1, I9 and main reservoir 4. At the sametime fluid under pressure flows from chamber I29 through passage IZI tochamber I I9, and when it is increased to substantially the same degreeas in the main reservoir 4, moves the piston I99 upward against the stopII8. When thepiston I99 occupies its upper position it is effectivethrough stem H2 and disc H3 to maintain the piston I29 and the stem I2'Iin a raised position in which the stem I21 is outof engagement with theexhaust valve I39 which permits spring I48 to seat the supply valve I49.With the stem I21 moved out of engagement with the exhaust valve I39 acommunication is established from the trailer brake cylinders I3 and I4to atmosphere through the branch pipes MM and I43b, pipe I43, chamberI29, past the open exhaust valve I39 through the bore I3I to chamber I23and thence through the exhaust port I24, whereby the brakes on thetrailer will be released.

Thus, with the pedal Ita in the brake release position, the brakes onboth the tractor and trailer will be released, and the brake pipe 1, I9and the trailer reservoir I2 will be charged with fluid under pressurefrom the main reservoir 4 on the tractor. I

If it is now desired to apply the brake on both the tractor and trailerat the same time, since the cock 2 is in its open position, the operatorwill depress foot pedal Ita to rock the operatinglever 19counterclockwise about Shaft 80, the right hand end of said lever movingthe sleeve 16 against spring 18 during such movement. As the left-handend of the operating lever 19 moves downward said lever acting throughthe lugs 49 on the spring cage 45 will correspondingly displace saidcage against spring 41 and increase the pressure of said spring againstpiston 34. When the pressure of spring 41 is increased to a degreesuiiicient to overcome the force of spring 44 acting beneath piston 34,said piston and stem 35 will move downward until said stem engages theexhaust valve 22 which closes the exhaust communication from the tractorbrake cylinders 5 and 9. Further downward movement of the left-hand endof the operating lever 19 will then cause the stem 2I to move theexhaust valve 22 downward to unseat supply valve28 and permit fluidunder pressure to flow from main reservoir 4 to the tractor brakecylinders 5 and 9 by way of pipe and passage 21; through chamber 26,past the unseated supply valve 28, through bore I8 to chamber 23 andthence through the pipe 39 and branch pipes 39a. and 39b for therebyapplying the tractor brakes. Fluid under pressure from chamber 23 alsoflows through the small passage 24 to chamber 25 beneath piston 34. Whenthe pressure beneath piston 34, together with the force of spring 44exceeds the downward pressure of spring 41 said piston and stem 35 willbe moved upward further compressing spring 41. Upward movement of stem35 permits spring 33 to move stem 2I upward maintaining the exhaustvalve 22 in contact with stem 35 until the supply valve 28 is seated,thus terminating the supply of fluid under pressure to the tractor brakecylinders 5 and E and chamber 25 and since the pressure of spring 41 isnow just counterbalanced movement of piston 34 will cease with therelease valve 22 still seated. Thus. it is seenthat the. pressure.obtained in the tractor brake cylinders. and 6 and chamber 25 is limitedin accordance, with the amount of pedal movement imparted to pedal I6aby the operator.

When it is desired toreduce the pressure in tractor brake cylinders 5and 6 the operator will reduce the foot pressure on pedal 16a to permitspring I8 to actuate aid lever to correspondingly reduce the pressure ofspring 41 on piston 34. The pressure of fluid in chamber 2.5 togetherwith the force of spring 44 will then move the piston 34 and stem35 awayfrom exhaust valve 22, which is held against movement by the seatedsupply valve 28, thus establishing a communication between the tractorbrake cylinders 5 and 6 and atmosphere in a manner hereinbeforeexplained for releasing fluid under pressure from said cylinders. At thesame time, fluid under pressure in chamber 25 beneath the piston 34will=be ermitted to flow through the small passage 24 to chamber 23 andto the atmosphere along with that from the truck brake cylinders 5 and6. When the pressure in the chamber 25 and beneath the piston 34 hasthus reduced sufficiently for the downward force of spring 41 acting onsaid piston to exceed the upward pressure acting thereon, said pistonand stem 35 will be moveddownward until said stem engages exhaust valve22 which terminates the release of fluid under pressure from truck brakecylinders 5 and 5 and thereby limits the reduction in such pressure to adegree corresponding to the position of pedal I6a.

Ifit is desired to completely release the brakes in the tractor andtrailer the operator will remove his foot-from pedal Ilia, to permitspring 13 to return lever I9 to the release position shown inthe drawingwhereupon the spring 4.? is permitted to expand to reduce the force onpiston 34 to a degree which is less than the opposing pressure of spring44, whereupon said opposing pressure will move piston 34 and stem 35upward away from the exhaust valve 22 to connect the tractor brakecylinders 5 and 5 to atmosphere in the manner hereinbefore described.The pressure in the tractor brake cylinders will then reduce toatmospheric pressure to permit a complete release of'the tractorbrakes.-

It is thus seen that fluid under pressure may be supplied to andreleased from the tractor brake cylinders for varying the pressuretherein and thereby the degree'of brake application on the tractor inaccordance with the position of foot pedal I6a. At the same time thatthe lefthand end of operating lever I9 is moved downward in response tofoot pressure applied to pedal Ilia for applying the brakes-on thetractor, the right hand end of said lever and sleeve :6 is moved upwardas above mentioned which permits spring 72 to expand, since as theflange I5 of spring cage I6 is moved upward, flange I3 of spring cage IIwill be moved upward therewith by the compressive force of spring 72 andwill remain in contact with flange F5. The resulting expansion of smallspring 12 reduces the pressure thereof on the upper side of pistont63.The brake pipe pressure present in chamber 56 and beneath piston 63 willthen be effective-to'move said piston and stem 64 upward which permitsspring 62 to move stem 52 upward maintaining the exhaust valve 53 seatedon stem 64 until supply valve 58 is seated thus terminating the supplyof fluid-under pressure from the main reservoir 4: to the-brake pipes. 1and It). Further upward movementof; piston .63 and stem 64 then movessaid stemaway from exhaust valve 53 to establish a communication frombrake pipe 1, In to the atmosphere through chamber 54, bore 65 in stem64; chamber 31, and slot 39 in cover 38. At the same time, brake pipepressure present inchamber 56 and beneath piston 63 will be permitted toflow through the small passage 55 to chamber 54 and to atmosphere alongwith that from the brake pipe I, ID. The brake pipe pressure will thusreduce until the pressure in chamber56 and beneath piston 63 is reducedto slightly below the force of spring 12 acting on the top of saidpiston at which time said piston and stem 64 will be moved downwarduntil said stem engages exhaust valve 53 which terminates the flow offluid under pressure from the brake pipe to the atmosphere. The pressurein the brake pipes I, I0 is thus reduced to a degree corresponding tothe depressed position of the pedal I6a.

When the pressure in the brake pipes 1, I0 is reduced as just described,a corresponding reduction in pressure will occur in chamber H9 of theautomatic control valve II on the trailer by reason of said chambersconnection to the brake pipe through passage I2I and chamber I20. Whenthe pressure in chamber H9 beneath piston I06 is reduced as explainedabove, the force of spring II! will move said piston downward thuspermitting expansion of said spring until the reduced force of saidspring balances the reduced brake pipe pressure retained in chamber I59.Thus the downward movement of piston I06 is in accordance with theamount of reduction in brake pipe pressure effected by the operation ofoperators control valve device I.

The downward movement of piston I06 permits spring M5 to move disc H3,rod II2, piston I26 and stem I21 downward maintaining said disc incontact with the top face of piston I06. As the stem I2! thus movesdownward it will first engage the exhaust valve I39 to closecommunication between the trailer brake cylinders I3 and I4 and chamberI29, and bore I3I in said stem which is open to atmosphere through portI24, and will then cause stem I38 to move downward to unseat supplyvalve I40 and permit fluid under pressure to flow from trailer reservoirI2 to the trailer. brake'cylinclers by way of pipe I42 chamber I35, pastthe unseated supply valve I, through bore I37 to chamber I29 and thencethroughpipe I43-and branches I430 and M31). F uid-under pressure fromchamber I29 also flows through the small passage I36 to chamber I25 andbeneath piston I26. When the pressure of fluid thus obtained beneathpiston I26 slightly exceeds the downward pressure of spring I I5 actingon saidpiston through rod H2 and disc II3, said piston and stem I21 willbe'moved upward compressing said spring until the pressure of saidspring balances the pressure acting beneath said piston.- Upwardmovement of stem I 2'! permits spring I48'to-move stem I38 upwardmaintaining exhaust valve I39 in contact with stem I21 until supplyvalve I 461s seated thus terminating the supply of fluid under pressureto the trailer brake cylinders I3 and I4. Thus it is seen that thepressure obtained in the trailer brake cylinders I3 and I4 is limited inaccordance with the amount of reduction in pressure in the brake pipe I,IIl-and'therefore in accordance with the positionof'the pedal I6a. Itwill further be seen tliat theistraight air portion I5a of theoperator's control. device and. the automatic portion I6 thereof operatein unison and that the brakes .on both the tractor and trailer will beapplied substantially in unison and tosubstantially the same degreecorresponding to the position of pedal I611.

It should be noted at this point that the disc check valve I45 preventsback flow of fluid-under pressure from the trailer reservoir I2 tochamber I20 and brake pipe 10 when the pressure of fluid in the brakepipe I, I is reduced to effect a brake application as described above,but permits said reservoir to be charged with fluid under pressure pastsaid disc checkvalve when the brake pipe pressure exceeds that insaidreservoir.

When the foot pressure on pedal Ilialis reduced to permit a returnthereof towardits nor mal or release position for releasing fluid underpressure from the tractor brake cylinders and 6, as above described, themain reservoir 4 will be connected to brake pipe 7, II] in a mannerhereinbefore described. As brake pipe pressure then increases inchamberI20 of the automatic control valve II, the disc check valve I45 will belifted from its seat against the force of spring I48 to permit thetrailer reservoir I2 to be recharged with fluid under pressure from thebrake pipe I0. At the same time, brake pipe pressure will be increasedin chamber H9 and beneath piston [06. When this pressure exceeds theforce of spring II I it will be effective to move said piston upwarduntil it moves into engagement with stop H8. The upward movement ofpiston I06 carries with it rod II2, piston I26, and stem I21 by reasonof the engagement of the upper face of piston I06 by the disc II3 whichis rigidly fastened to rod H2. The upward movement of stem I21 movessaid stem away from exhaust valve I39 thus establishing thecommunication from trailer brake cylinders I3 and I4 to atmosphere forreleasing the fluid under pressure from said cylinders for in turnreleasing the trailer brakes.

From the foregoing it is seen that when the operator depresses footpedal Ilia fluid will be supplied to both the truck and trailer brakecylinders at a pressure substantially proportional to the amount ofdepression of said pedal from its release position and when the operatorreleases the foot pressure on said pedal, the pressure of fluid in boththe truck and trailer brake cylinders will be reduced in accordance withthe change in position of said pedal.

When the trailer is empty it may be desired to prevent an application ofthe trailer brakes when the brakes on the tractor are applied, since thetractor brakes will be suflicient to properly control both vehiclesunder this condition. For safety sake, it is, however, desirable thatthe trailer brakes will be automatically applied in the event of thetrailer breaking loose from the tractor or rupturing of the hoseconnection between said tractor and trailer in order that the trailerwill be promptly stopped to avoid wrecking thereof.

To secure braking on the tractor only and yet provide for braking on thetrailer in case of a break in two or a rupture of the hose between thetractor and trailer, it is merely necessary to move handle 89 of cutoutcock 2 clockwise to the position indicated on the drawing by the dot anddash line 8%. In this position of handle 89 flow of fiuid under pressurefrom main reservoir 4 on the tractor through cut-out cock 2 to thetrailer brake pipe II] and the automatic control valve II on the traileris interrupted, but the ill) trailer reservoir I2 will be charged frommain reservoir! 'on the tractor through the check valve 3,c'onnectedin'by-passing relation to the cut-out cock 2. When the trailer reservoirthus becomes charged to substantially the pressure in the tractorreservoir 4 and in brake pipe I ahead of the cock 2, spring 99 will seatthe check valve 91 to prevent reverse flow from the trailer brake pipeIt to the operators control device I.

When, with the, cock 2 closed, the operator depresses'foot pedal Ifia toapply the tractor brakes the pressure in brake pipe l at the left handside of cut-out cock 2 will be reduced in the same manner as beforedescribed but the closed check valve 91 will preventfiow of fluid underpressure from the trailer brake pipe it and therefore prevent a brakeapplication on the trailer. If however the coupling between the tractorand trailer becomes seamstress hose ruptured'from any cause, therewillbe a rapid reduction in pressure in the trailer brake pipe II) whichwill cause operation of the'autom atic control valve I I toeifect anapplication of the trailer brakes in the same manner as hereinbeforedescribed.

It will now beseen that at the will of the operator fluid" underpressure may be admitted to both thetractor and trailer brake cylinderssimultaneously, or to the tractor brake cylinders alone which may bedesirable when no load is being carried on the trailer.

It will further be noted that even when the trailer is loaded and thecock 2 open, if the hose between the tractor and trailer should breakfor any reason the trailer brakes will be automatically applied.

Having now described my invention, What I claim as new and desire tosecure by Letters Patent, is:

1. In combination, first and second control pipes, a main reservoir andan operators control means, said operators control means comprising acasing having a chamber charged with fluid under pressure from said mainreservoir, two self-lapping valve means for supplying fluid underpressure from said chamber to said first and second control pipesrespectively, a pair of springs operative in response to an increase inforce thereof to render said self-lapping valve means effective tosupply fluid under pressure to said control pipes, a third springoperative in an expanded position to compress one of said pair ofsprings to render one of said self-lapping valve means operative tosupply fluid under pressure to said first control pipe, a shaft carriedby said casing, a control lever carried by said shaft and rockable tocompress the other said pair of springs and said third spring, to renderthe other of said self-lapping valve means operative to supply fluidunder pressure to said second control pipe and to render said oneself-lapping valve means operative to reduce the pressure in said firstcontrol pipe, and means for rocking said control lever.

2. A combined straight-air and automatic operators control means fortractor-trailer vehicles comprising a casing having a pair of chambers,a first control pipe connected to one of said chambers, a second controlpipe connected to the other of said chambers, supply valve means forsupplying fluid under pressure to each of said chambers and exhaustvalve means for releasing fluid under pressure from each of saidchambers, spring means for closing each of said supply valve means, ashaft carried by said casing, a rockable lever mounted on said shaft, a,spring disposed be- 11 tweenisaid lever and one-of'said exhaust valvemeans for providing a yieldable connection-between said lever and saidone exhaust .valve means, a second springfor maintaining. saidoneexhaust valve means in-a release position, a spring cage, a third springdisposed between the other of said exhaust valve means and said springcage for maintaining the said other exhaust valve means closed and thone .of :said supply valve means associated with said other exhaustvalve means open to supply fluid under pressure to one of said chambersand said first control pipe, and a fourth spring disposed between saidspring cage and said'casing for normally maintaining said thirdmentioned spring under compression, said rockable lever being rockableabout said shaft for increasing the compression of said one, said secondand said fourth mentioned springs and decreasing the compression on saidthird mentionedspring to close the said one exhaust valve means and openthe said other supply valve means and to close said onesupply valvemeans and open the said other exhaust valve means, and manual means forrocking said lever about said shaft.

NORMAN G. CADMAN.

12 REFERENCES I CITED "The following references are of record-in thefile of this patent:

UNITED STATES PATENTS Number Name Date 552,793 Stoner Jan. 7, 1896735,544 Mann Aug. 4, .1903 811,765 Corey Feb. 6, 1906 962,517 McElroyJune 28, 1910 1,218,479 Savio Mar. 6, 1917 1,827,849 Kazenmaier Oct. 20,1931 1,940,550 K-azenmaier Dec. 19, 1933 1,957,891 Kazenmaier May 8,1934 2,289,559 Turek Jul 14,1942 2,324,690 Gardiner et a1 July 20, 19432,329,742 Bush et al. Sept. 21, 1943 2,392,729 Edge Jan. 8, 1946

